Acoustic neuroma; early diagnosis

Hearing preservation after acoustic neuroma surgery

Acoustic neuromas (AN) are benign tumors that arise from the vestibular nerve within the internal auditory canal, where hearing loss is the most common symptom. This retrospective study was done to determine the results of hearing preservation in patients operated for AN at the University of Minnesota, as well as the factors affecting them. One hundred-eighty patients with AN were operated between 1988 and 1998, of whom 91 (50.5%) underwent hearing preservation surgery by either the middle fossa (MF) or the suboccipital (SO) approach. Preoperative and postoperative pure-tone averages (1, 2, and 4 K), speech discrimination scores (SDS), and acoustic reflex thresholds (ART) were noted and classified according to the Shelton's and the Gardner's classifications. The overall rate of hearing preservation was 23.1%. The outcome of hearing results was better with the MF approach compared with the SO approach. Small tumor size and better preoperative hearing levels favored a better postoperative hearing result. The rate of hearing improvement over time was better for the MF patients. Patients for whom intraoperative auditory monitoring was performed seemed to have better hearing outcomes.

Hearing preservation after microsurgical resection of large vestibular schwannomas

BACKGROUND

Hearing, which is often still clinically useful at presentation even with larger tumors, is a major determinant of quality of life in vestibular schwannoma (VS) patients.

OBJECTIVE

To present the hearing preservation rate after surgery in patients with large (>or=3 cm) VSs and identify clinical or radiologic predictors of hearing preservation.

METHODS

From April 2003 to March 2009, 192 patients underwent resection of a VS, including 46 large (>or=3 cm) tumors, of whom 28 had serviceable hearing preoperatively. Six of 28 patients (21.4%) had preserved hearing postoperatively.

RESULTS

Mean tumor diameter was 3.6 cm (range, 3.0-5.0 cm) and tumor volume was 17.2 mL (range, 6.9-45.2 mL). For patients with grade A Sanna-Fukushima hearing, the hearing preservation rate was 4 of 11 (36.4%). Complete resection was achieved in 6 of 6 cases with hearing preservation (41/47 for all patients). Six of 6 patients with preserved hearing had a cerebrospinal fluid cleft in the internal auditory canal (IAC) compared with 9 of 16 patients without preoperative hearing and 9 of 20 for patients with serviceable hearing that was lost postoperatively (P=.045). Six of 6 patients with preserved hearing had less than 35% of the tumor anterior to the longitudinal axis of the IAC compared with 13 of 20 in the serviceable hearing that was lost group (P=.036).

CONCLUSION

Our series demonstrates hearing preservation is possible for patients with large VSs and should be attempted in all patients with preoperative hearing. The quality of preoperative hearing, a cerebrospinal fluid cleft at the apex of the IAC, and a smaller proportion of tumor anterior to the IAC were positively associated with hearing preservation.

Hearing preservation in surgery for large vestibular schwannomas

OBJECT

Hearing preservation remains a challenging problem in vestibular schwannoma (VS) surgery. The ability to preserve hearing in patients with large tumors is subject to particular difficulty. In this study, the authors focus on hearing preservation in patients harboring large VSs.

METHODS

A total of 344 consecutive patients underwent surgical removal of VSs over the past 9 years. Of these 344 cases, 195 VSs were > 20 mm in maximum cisternal diameter. Of the 195 cases, hearing preservation surgery was attempted for 54 patients who had a Class A, B, C, or D preoperative hearing level; that is, a pure tone average <or= 60 dB and speech discrimination score >or= 50% according to the Sanna/Fukushima classification. The tumors were classified as moderately large (21-30 mm based on the largest extrameatal diameter), large (31-40 mm), and giant (>or= 41 mm) according to the international criteria. The authors categorized patients with Class A, B, C, D, or E hearing (pure tone average <or= 80 dB and speech discrimination score >or= 40%) as having preserved hearing postoperatively.

RESULTS

Forty-one tumors (75.9%) were totally removed and 13 (24.1%) had near-total removal. Of the 54 patients, 29 maintained their hearing postoperatively; the overall hearing preservation rate was 53.7%. Analysis based on the preoperative hearing level showed that hearing was preserved in 14 (77.8%) of 18 cases for Class A; in 8 (47.1%) of 17 cases for Class B; in 4 (57.1%) of 7 cases for Class C; and in 3 (25.0%) of 12 cases for Class D. In addition, according to the analysis based on the tumor size, 20 (52.6%) of 38 patients with moderately large tumors retained their hearing, as did 5 (50.0%) of 10 patients with large tumors and 4 (66.7%) of 6 patients with giant tumors. Complications included 2 cases of bacterial meningitis that were cured by intravenous injection of antibiotics, 3 cases of subcutaneous CSF leakage that resolved without any surgical repair, and 1 case of temporary abducent nerve palsy. There were no deaths in this series.

CONCLUSIONS

The results indicate that successful hearing preservation surgery in large VSs is possible with meticulous technique and attention to adhesions between the tumor and the cochlear nerves.

Hearing preservation and facial nerve function after microsurgery for intracanalicular vestibular schwannomas: comparison of middle fossa and retrosigmoid approaches

PURPOSE

Therapeutic options for vestibular schwannomas (VS) include microsurgery, stereotactic radiosurgery and conservative management. Early treatment of intracanalicular vestibular schwannomas (IVS) may be advisable because their spontaneous course will show hearing loss in most cases. Advanced microsurgical techniques and continuous intraoperative monitoring of cranial nerves may allow hearing preservation (HP) without facial nerve damage. However, there are still controversies about the definition of hearing preservation, and the best surgical approach that should be used.

METHODS

In this study, we reviewed the main data from the recent literature on IVS surgery and compared hearing, facial function and complication rates after the retrosigmoid (RS) and middle fossa (MF) approaches, respectively.

RESULTS

The results showed that the average HP rate after IVS surgery ranged from 58% (RS) to 62% (MF). HP varied widely depending on the audiometric criteria that were used for definition of serviceable hearing. There was a trend to show that the MF approach offered a better quality of postoperative hearing (not statistically significant), whereas the RS approach offered a better facial nerve preservation and fewer complications (not statistically significant).

CONCLUSIONS

We believe that the timing of treatment in the course of the disease and selection between radiosurgical versus microsurgical procedure are key issues in the management of IVS. Preservation of hearing and good facial nerve function in surgery for VS is a reasonable goal for many patients with intracanalicular tumors and serviceable hearing. Once open surgery has been decided, selection of the approach mainly depends on individual anatomical considerations and experience of the surgeon.

Standardized format for depicting hearing preservation results in the management of acoustic neuroma

The Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery recently published guidelines for reporting hearing preservation in the treatment of acoustic neuromas. These suggestions included pretreatment and posttreatment pure-tone hearing thresholds, word recognition scores, and hearing classification. We present a standardized reporting format that addresses the Committee's recommendations and displays individual patient audiologic data as a simple, concise plot of posttreatment hearing results. To illustrate the use of the recommended format, preoperative and postoperative hearing data from our institution are reported. Such reporting criteria will facilitate comparative reviews of studies of hearing preservation after surgical or radiotherapeutic management of acoustic neuromas, while providing specific data for individual patient outcome analysis.

Acoustic neuroma surgery: absent auditory brainstem response does not contraindicate attempted hearing preservation

OBJECTIVE

Absence of auditory brainstem response (ABR) waveforms has been associated with a poor likelihood of hearing preservation following resection of acoustic neuromas. Our experience is reviewed for patients with absent preoperative ABR regarding hearing preservation, hearing improvement, and return of ABR.

STUDY DESIGN

Retrospective review of 22 cases of acoustic neuroma resection. Nine patients with absent preoperative ABR were identified. All underwent tumor resection utilizing intraoperative cochlear nerve action potential (CNAP) monitoring. Postoperative hearing results and ABR waveforms were examined.

METHODS

Charts were reviewed and tabulated for age, sex, tumor side, tumor size, preoperative and postoperative audiometric and ABR results, intraoperative monitoring results by ABR and CNAP, and surgical complications.

RESULTS

Hearing preservation was achieved in seven of nine patients (78%) with absent preoperative ABR, as well as six of seven patients (86%) with tumors less than or equal to 20 mm in greatest dimension. Although intraoperative ABR monitoring was not possible in any of these patients, CNAP monitoring was successful in all. Return of ABR waveforms was observed in four of the six patients (67%) tested from 3 to 22 months postoperatively. Four of the seven patients (57%) enjoyed improvement in hearing class as defined by the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery.

CONCLUSIONS

Absent ABR waveforms have not been a negative prognostic sign regarding hearing preservation. CNAP monitoring is possible in these patients and likely helps to minimize iatrogenic cochlear nerve trauma. Patients with no ABR waveforms have hope of hearing preservation and even improvement following acoustic neuroma resection performed utilizing CNAP monitoring and hearing preservation surgical techniques.

Hearing preservation in patients undergoing vestibular schwannoma surgery: comparison of middle fossa and retrosigmoid approaches

OBJECT

The goal of this retrospective study was to evaluate hearing preservation after surgery for vestibular schwannoma in which the middle fossa (MF) or retrosigmoid (RS) approaches were used. Hearing preservation in vestibular schwannoma surgery can be achieved by using either the MR or RS approach. Comparative outcome data between these approaches are lacking, and, as a result, selection has generally been determined by the surgeon's preference.

METHODS

The authors have compared removal of small vestibular schwannomas via MF and RS approaches with regard to hearing preservation and facial nerve function. The study group was composed of consecutively treated patients with vestibular schwannoma, 48 of whom underwent operation via an MF approach and 50 of whom underwent the same number of RS operations. Tumors were divided into size-matched groups. Hearing results were recorded according to the American Academy of Otolaryngology-Head and Neck Surgery criteria, and facial nerve outcome was recorded as the House-Brackmann grade. Overall, 26 (52%) of the patients treated via the MF approach achieved a Class B or better hearing result compared with seven (14%) of the RS group. Some hearing was preserved in 32 (64%) of the patients in the MF group and in 17 (34%) of the RS group. The results obtained by using the MF approach were superior for intracanalicular tumors (p=0.009, t-test), and for tumors with a cerebellopontine angle (CPA) component measuring 0.1 to 1 cm (p=0.006, t-test). For tumors in the CPA that were 1.1 to 2 cm in size, our data were inconclusive because of the small sample size. Facial weakness was seen more frequently after MF surgery in the early postoperative period, but results were equal at 1 year.

CONCLUSIONS

The results of this study have demonstrated a more favorable hearing outcome for patients with intracanalicular tumors and tumors extending up to 1 cm into the CPA that were removed via the MF when compared with the RS approach.

Preservation of hearing in surgery for acoustic neuromas

Preservation of hearing was attempted in 161 cases of histologically confirmed acoustic neuroma removed by the senior author between January 1, 1970, and September 30, 1991. There were 136 patients with unilateral tumors; 22 patients had bilateral tumors (neurofibromatosis 2) and underwent a total of 25 procedures. Hearing was initially preserved in 35% of patients with unilateral tumors and in 44% of those with bilateral tumors. Results are reported in terms of pre- and postoperative pure tone average and speech discrimination scores. Surgical access to the tumor was obtained via middle cranial fossa and suboccipital approaches. The latter has been used more often over the past 5 years because of a lower associated incidence of transient facial paresis. Persistent postoperative headaches have been the most common complication following the suboccipital approach. The results of preoperative brain-stem auditory evoked response (BAER) studies were useful in predicting the outcome of hearing preservation attempts. Patients with intact BAER waveform morphology and normal or delayed latencies had a higher probability of hearing preservation in comparison to those with abnormal preoperative BAER morphology.

Type 2 neurofibromatosis: the need for supraregional care?

The results of a U.K. study of 145 cases of type 2 neurofibromatosis has shown generally very poor operative results in terms of hearing and facial nerve preservation. Only 9 out of 118 vestibular schwannoma (acoustic neuroma) operations resulted in any clinically detectable hearing preservation and only 32 left the patient with good or normal (House grade I or II) ipsilateral facial nerve function. Although operation is still the definitive treatment of vestibular schwannoma (acoustic neuroma) and may be a lifesaving procedure, it appears that the evidence in favour of early operation is only valid when carried out in highly specialized centres. The special problems of NF2 cases who may go on to develop multiple spinal and cranial tumours making them wheelchair bound and blind as well as deaf warrants a careful experienced approach. Timing of operations may be critical for the enhancement of useful years of quality life. We therefore propose the setting up of a national NF2 register, with the management of cases at a few supraregional centres.

Preoperative findings and hearing preservation in acoustic neuroma surgery

For the purpose of clarifying whether or not the possibility of hearing preservation can be predicted preoperatively, we compared clinical characteristics and preoperative test results between hearing preserved and hearing unpreserved patients. Based on an analysis of this study, we conclude that duration of symptoms, ABR findings and caloric test results, in addition to hearing level, speech discrimination score and tumor size should be considered as prognostic signs of hearing preservation. Although all factors do not suggest a definite possibility of hearing preservation, candidates for hearing preservation surgery should be selected according to these prognostic factors.

Hearing preservation in unilateral acoustic neuroma surgery

This paper reviews the principal English literature on hearing preservation in unilateral acoustic neuroma surgery. Seventeen case reports and 13 surgical series are included. In addition, we report ten cases of our own, two with successful hearing preservation. The purpose of this report is to study feasibility, success rate, and associated problems. Previous reports have been compared in terms of criteria that we have selected. A classification system similar to Silverstein's is used. The total number of cases under review is 621, with 221 reported successes. Cases limited to those having a unilateral acoustic neuroma, with valid supportive audiometry, were 394, with 131 successes. The approximate overall rate of success is 33%. There are five cases of hearing preservation with unilateral acoustic neuromas 3 cm or larger when supporting audiometric data are available, the largest being "4-5 centimeters." Problems included mixing of unilateral acoustic neuromas with other types of tumors and failure to include comprehensive data, particularly audiometry. We conclude 1) that hearing preservation is a reasonable goal in unilateral acoustic neuroma surgery, although the number of available candidates is relatively small and 2) that intelligent selection of patients and high quality surgical technique are the keys to success.

Preservation of hearing in patients undergoing excision of acoustic neuromas and other cerebellopontine angle tumors

Microsurgical techniques have made it possible to identify and preserve the cochlear nerve from its origin at the brain stem and along its course through the internal auditory canal in patients undergoing removal of small or medium-sized acoustic neuromas or other cerebellopontine angle (CPA) tumors. In a consecutive series of 100 patients with such tumors operated on between 1975 and 1981, an attempt was made to preserve the cochlear nerve in 23. The decision to attempt to preserve hearing was based on tumor size and the degree of associated hearing loss. In cases of unilateral acoustic neuroma, the criteria for attempted preservation of hearing were tumor size (2.5 cm or less), speech reception threshold (50 dB or less), and speech discrimination score (60% or greater). In patients with bilateral acoustic neuromas or tumors of other types, the size and hearing criteria were significantly broadened. All patients were operated on through a suboccipital approach. Hearing was preserved postoperatively in six (31.6%) of the 19 patients with unilateral acoustic neuromas, although the cochlear nerve was preserved in 16. Of the six patients with postoperative hearing, three retained excellent hearing, and the other three had only sound awareness and poor discrimination. Hearing was preserved in three cases with other CPA tumors, including an epidermoid cyst and small petrous meningiomas in the internal auditory canal. Of the two cases with bilateral tumors, hearing was preserved in one. Of the 23 patients in whom hearing preservation was attempted, nine (39.1%) had some postoperative hearing, which in six was equal to or better than the preoperative level. Thus, it is worthwhile to attempt hearing preservation in selected patients with CPA tumors.

Technique of hearing preservation in small acoustic neuromas

The ideal operation for acoustic neurinoma would not only provide total excision without injury to the brain stem and with preservation of facial nerve function, but would also allow retention of useful hearing in those patients who come to operation with intact hearing function. Documented preservation of useful hearing in the rather extensive literature concerning acoustic neurinomas is rare. An operative technique has been developed utilizing a retromastoid approach, brain stem auditory-evoked potentials and direct auditory monitoring, facial nerve electromyography, and microsurgical techniques that have enabled us to preserve useful hearing in three and some hearing in two of six consecutive patients who had preoperative hearing. Rules regarding preservation and criteria regarding documentation of hearing preservation are outlined.

Preservation of facial and acoustic nerves in the total removal of large and small acoustic tumors. Report of two cases

Two cases are presented in which an acoustic tumor was totally removed without the aid of an operating microscope. In one of them, a large lesion was excised, with restoration of the patient's hearing postoperatively. The anatomical problems are analyzed, and the relevant literature is reviewed briefly.

A comparative study of special petrous views and tomography in the diagnosis of acoustic neuromas

A review is presented of the value of special petrous views and tomography in 56 patients with acoustic neuromas. Ninety-two per cent of these patients showed abnormality of the petrous bones. Tomography was found to be only slightly more productive than special plain film views of the petrous pyramids in terms of positive diagnosis, and it gave rise to an increased incidence of false positives. For this reason, and to reduce unnecessary exposure, it is recommended that tomography of the internal auditory canals should be considered only after a careful study of adequate plain radiographs, which may themselves be diagnostic. In 73 per cent of the patients in this series the diagnosis could be made with a single slit perorbital projection.